Animating height property

问题

Hello there stackoverflow and nativescript users!

I have a problem with animating a view.

What I want: I am trying to create a view where you can click and it opens op a new view below animated pushing all other views further down.

Problem: Only the elements inside are animated or nothing is animated at all.

What I tried: I tried using the nativescript UI Animations but without success because the height property is not supported.

My version: https://gyazo.com/130c2b3467656bcc104c9b8e2c860d94

I would love to hear the solutions you all have come up with to tackle this.

回答1:

You can use tweenjs in your nativescript application defining the following class which rely on tweenjs (install it with npm i @tweenjs/tween.js)

import * as TWEEN from '@tweenjs/tween.js';
export { Easing } from '@tweenjs/tween.js';

TWEEN.now = function () {
    return new Date().getTime();
};

export class Animation extends TWEEN.Tween {
    constructor(obj) {
        super(obj);
        this['_onCompleteCallback'] = function() {
            cancelAnimationFrame();
        };
    }
    start(time) {
        startAnimationFrame();
        return super.start(time);
    }
}

let animationFrameRunning = false;
const cancelAnimationFrame = function() {
    runningTweens--;
    if (animationFrameRunning && runningTweens === 0) {
        animationFrameRunning = false;
    }
};

let runningTweens = 0;
const startAnimationFrame = function() {
    runningTweens++;
    if (!animationFrameRunning) {
        animationFrameRunning = true;
        tAnimate();
    }
};
const requestAnimationFrame = function(cb) {
    return setTimeout(cb, 1000 / 60);
};
function tAnimate() {
    if (animationFrameRunning) {
        requestAnimationFrame(tAnimate);
        TWEEN.update();
    }
}

Then, to animate the height of a view you can use a method like this (this one works in nativescript-vue but you just have to adapt the way you retrieve your view object) :

import {Animation, Easing} from "./Animation"

toggle() {
    let view = this.$refs.panel.nativeView
    if (this.showPanel) {
        new Animation({ height: this.fixedHeight })
            .to({ height: 0 }, 500)
            .easing(Easing.Back.In)
            .onUpdate(obj => {
                view.originY = 0
                view.scaleY = obj.height / this.fixedHeight;
                view.height = obj.height;
            })
            .start()
            .onComplete(() => this.showPanel = !this.showPanel);
    } else {
        this.showPanel = !this.showPanel
        new Animation({ height: 0 })
            .to({ height: this.fixedHeight }, 500)
            .easing(Easing.Back.Out)
            .onUpdate(obj => {
                view.originY = 0
                view.scaleY = obj.height / this.fixedHeight;
                view.height = obj.height;
            })
            .start();
    }
}

This was discussed here : https://github.com/NativeScript/NativeScript/issues/1764 I mainly improved the onUpdate to have a smooth animation

来源：https://stackoverflow.com/questions/53105091/animating-height-property

标签

nativescript

nativescript-vue